The embodiments herein generally relate to transistor structures and more particularly to structures that induce channel strain to meet performance targets by incorporating tunable amounts of germanium (Ge) to enhance hole mobility and achieve threshold voltage (Vt) modulation.
A fin-type field effect transistor (FinFET) is a transistor that is formed within a fin of material. A fin is a relatively narrow width, relatively tall height structure that protrudes from the top surface of a substrate. The fin width is intentionally kept small to limit the short channel effect. A fin cap is positioned on the top of the fin and runs along the fin length. The fin cap has a fin cap width equal to the fin width, and fin cap height that is less than the fin height.
In a FinFET, a gate conductor is positioned on the top surface of the substrate and over a portion of the fin. The gate conductor runs parallel to the top of the substrate and is perpendicular to the fin length such that the gate conductor intersects a portion of the fin. An insulator (e.g., gate oxide) separates the gate conductor from the fin and the fin cap. Further, the region of the fin that is positioned below the gate conductor comprises a semiconductor channel region. The FinFET structure can include multiple fins and fin caps, in which case the gate conductor would wrap around, as well as fill in, the space between these fins.